The A9W21325 is an add-on residual current device (RCD) from the Schneider Electric Acti9 Vigi iC60 range, designed to clip onto the outgoing side of an iC60 MCB with double terminals. It provides earth leakage protection for the downstream circuit without taking up extra DIN-rail space — the unit mounts directly onto the breaker via the screw connection. Rated 25 A with 30 mA sensitivity, Type A, instantaneous trip. The 30 mA threshold is the standard for personal protection against indirect contact in most IEC 60364 installations; it clears a fault before ventricular fibrillation becomes a risk.
The tunnel-type terminals on the downside accept 1...25 mm² rigid or 1...16 mm² flexible cable; strip length 14 mm, tighten to 2 N·m. IP20 body, IP40 within a modular enclosure — fine for a closed panel, not for washdown areas. The voltage-independent residual current tripping technology means the RCD operates without needing an external power supply — it uses the fault energy itself to trip. That's a reliability advantage in installations where a neutral loss could otherwise leave a powered RCD blind.